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Complexes [MCl2Cp*]2 (M=Ir, Rh), [RuCl2(p‐cymene)]2 and [Ir(C^N)2Cl]2 (HC^N=a, phenylpyridine ; b, phenylpyrazole,) react with imine ligands derived from ο‐aminophenol to yield complexes with an exocyclic C=N bond which has a cis or trans configuration. The trans isomer is favoured except for sterically crowded complexes Cp*M (M=Ir, Rh) when the imine has a mesityl substituent, for which the cis isomer is favoured. The complexes undergo photoisomerisation in visible light but revert back to the original isomer over time or when heated. The rate of the thermal reverse isomerisation depends on the imine substituent and the metal fragment. DFT calculations correctly reproduce the favoured isomer and suggest that the reverse isomerisation occurs by a rehybridisation at the N atom as found in organic imines. In addition, a triplet state, thermally accessible by a Minimum Energy Crossing Point (MECP) provides a low energy pathway for reverse isomerisation in the case of the half‐sandwich complexes. [ABSTRACT FROM AUTHOR]

Metal‐metal bonds have rarely been explored as active elements in supramolecular assemblies despite their unique potential to introduce responsive behavior. In this report, a dynamic molecular container composed of two cyclometalated Pt units is constructed using Pt−Pt bonds. This molecule—the flytrap—has a flexible jaw composed of two [18]crown‐6 ethers that can adapt their shape to bind large inorganic cations with sub‐micromolar affinity. Along with the spectroscopic and crystallographic characterization of the flytrap, we report its photochemical assembly, which allows the capture of ions and their transport from solution to the solid state. In addition, we have been able to recycle the flytrap to regenerate its starting material due to the reversible nature of the Pt−Pt bond. We believe that other molecular containers and materials for harvesting valuable substrates from solution could be assembled using the advances presented here. [ABSTRACT FROM AUTHOR]

Macrocycle engineering is a key topic in supramolecular chemistry. When synthesizing a ring, one can obtain either complex mixtures of macrocycles of different sizes or a single ring if a template is utilized. Here, we unite these approaches along with post‐synthetic modifications to transform a single tether into multiple rings—up to five per tether. The macrocycles contain two bridged phenylpyridine ligands that are connected through a Pt atom, which defines the rings' shape, size, and host activity. All rings undergo redox reactions (between PtII and PtIV) that allow for large conformational changes. Their reactivity, together with their host performance, is a convenient way to control the capture and release of guests, to mediate ring transformations, and to control pseudorotaxane‐to‐pseudorotaxane conversions. This novel approach could serve to assemble other libraries of small ring molecules, create cyclic polymers bridged by responsive‐at‐metal nodes, and produce processable mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

A computational investigation about the Lewis acid-base adducts between bases [Cp.sub.2]M[H.sub.2] (M = Mo, W) and acids B[X.sub.3] (X = F, Cl) and [Al([CH.sub.3].sub.3] is presented. Density functional methods based on pure and hybrid correlation-exchange functionals and relativistic corrections based on the zero order relativistic approximation (ZORA) have been applied. A comparison with experimental data has been addressed to give insights about the nature of the acid-base interaction with the aim to evaluate the role of the transition metal in charge donation toward the acid centre. In this respect, the likelihood of proposed criteria for recognizing the presence of transition-metal direct charge donation has been discussed. Key words: metallocenes, Lewis basicity, density functional theory (DFT), atoms in molecules (AIM), zero order relativistic approximation (ZORA). On a effectue une etude theorique des adduits acide-base de Lewis entre les bases [Cp.sub.2]M[H.sub.2] (M = Mo, W) et les acides B[X.sub.3] (X = F, Cl) et [Al([CH.sub.3].sub.3]. On a utilise les methodes de la fonctionnelle de la densite en faisant appel a des fonctionnelles de correlation-echange pures ainsi qu'hybrides et on a applique des corrections relativistes basees sur l'approximation relativiste d'ordre zero (AROZ). Une comparaison avec les donnees experimentales a ete realisee afin d'obtenir des informations sur la nature de l'interaction acide-base qui permettraient d'evaluer le role du metal de transition dans le transfert de charge vers le centre acide. Dans cette optique, on discute du potentiel d'utilite des criteres proposes pour reconnay tre la presence d'un transfert de charge direct de la part du metal de transition. Mots-cles : metallocenes, basicite de Lewis, theorie de la fonctionnelle de la densite (TFD), atomes dans une molecule << AIM >>, approximation relativiste d'ordre zero (AROZ). [Traduit par la Redaction], Introduction The acid-base adduct between bis(cyclopentadienyl)dihydridotungsten ([Cp.sub.2]W[H.sub.2]) and B[F.sub.3] was firstly communicated by Shriver (1) in 1963. It represented one of the first (and representative) examples of Lewis base behaviour [...]

The synthesis and the full spectroscopic characterization (FT-IR, FT- Raman, [sup.31]P CP MAS NMR) of trans-bis[O-ethyl-phenylphosphonodithioato][Ni.sup.II] (3) are reported. On the basis of hybrid-Density Functional Theory (DFT) calculations and Extended Huckel Theory (EHT) calculations, performed on the simpler trans-bis[O-methyl-phenylphosphonodithioato][Ni.sup.II] (2) model complex, the electronic structures of phosphonodithioato complexes in their ground states are fully described, and in particular the vibrational features are deeply analyzed, allowing an unprecedented insight into the vibrational features of trans-bis-O-methyl-phenylphosphono- and trans-bis(isopropylamidophosphono)-dithioato complexes of nickel(II), palladium(II), and platinum(II). Key words: phosphonodithioato complexes, IR, Raman, DFT calculation.

The syntheses of the first examples of selenoparabanic acid derivatives (dialkylimidazolidine-2-selone-4,5-dione, [3e.sup.R], R = Me, Et, Bu) are presented along with the X-ray crystal structure determination of 3[e.sup.Et]. To gain an insight in the properties of parabanic acid derivatives on the basis of their electronic structures, we report the results of comparative hybrid-DFT calculations performed on parabanic, thioparabanic, and selenoparabanic acids ([3a.sup.H], [3b.sup.H], and [3e.sup.H] and on their N,N'-dimethyl derivatives [3a.sup.Me], [3b.sup.Me], and [3e.sup.Me]. Calculations show that the different nature of the frontier orbitals of [3a.sup.R] compared to those of [3b.sup.R] and [3e.sup.R], might account for the different reactivities of these compounds. Moreover, the weak donor character of [3b.sup.R] and [3e.sup.R] towards molecular di-iodine, estimated by FT-Raman measurements is in agreement with the calculated NBO-charge distribution. Key words: selenation, selenoparabanic derivatives, crystal structure, DFT calculations.

Molecular dynamics simulations at atomistic level have been performed on a metal-porphyrazine complex. Starting from an isotropic state, the system was cooled until transition from isotropic to columnar phase was observed; no nematic phase was encountered. Many tools were utilized to follow the system evolution: order parameter, g(r), g∥(r∥), gc(r∥), g⊥(r⊥), g2(r), also density and energy changes. Very long runs were required to get reliable results, times greater than 40 ns of simulation. The structure of columnar phase was analyzed and the organization of molecules in the columns was investigated, along with the role of conformation of side chains. We found that in columnar phase the molecules are tilted versus the column axis and the conformation of side chains changes during the phase transition to allow this kind of organization; moreover the direction of columns axes is different from that of the director. [ABSTRACT FROM AUTHOR]

A family of molecular heptacadmium carboxylate clusters templated inside [3+3] Schiff base macrocycles is isolated and analyzed by variable temperature solution and solid-state NMR spectroscopy, single-crystal X-ray diffraction (SCXRD), and density functional theory (DFT) calculations. The studies have helped in understanding the host-guest and dynamics properties of a new family of metallocavitands and have helped in designing new supramolecular catalysts and materials.

The form of 8-hydroxyquinoline in different solvents is examined by using spectroscopic and computational methods. The results have shown that 8-hydroxyquinoline has displayed a clear preference for the cis conformation, but a small fraction of the trans conformation is present in water solutions.

The synthesis, characterization and photoreactivity of a series of new heteroaryl imines form the coupling between 2-benzothienyldiphenylmethyliminophosphorane and heterocyclic aldehydes are described. The reaction at 60 degree Celsius gave the formation of only the trans isomer while at high temperature cis isomer was obtained and only the cis isomers showed a photochemical reactivity to give corresponding condensed pyridine derivative.

Nonrelativistic and relativistic time-dependent density functional calculations are performed on the excited states of the [M(H2timdt)(sub 2)] (M = Ni, Pd, Pt) compounds. In all members of the series, the excited state at the lowest energy corresponds to a HOMO -> LUMO excitation and indicates that a large number of the transitions have an intraligand character.

Research has been conducted on 2,3-epoxy alcohols. The authors describe their study of the role of metal ions in regioselective opening of these alcohols carried out via hybrid density functional theory method.

Density functional theory and time-dependent density functional theory were applied to describe the ground and excited states and the spectral characteristics of the meridianal and facial isomers of aluminum tris(quinolin-8-oclate) (Alq3). Experimental meridinal Alq3 absorption band locations were well reproduced by the computations, which allowed easy assignment of the absorption bands.

The results of a systematic density functional study, carried out using a self-consistent hybrid approach including exact exchange contribution, on the all monocarbonyls of first-row transition metals, are reported. Geometries, harmonic wave numbers, and binding energies, obtained using both standard generalized gradient corrected and hybrid functionals, are compared with previous published theoretical data and the available experimental findings. It is shown that hybrid functionals give results close to highly correlated post Hartree–Fock approaches and which are sensibly different from those obtained by standard local, even gradient corrected, methods. A nice agreement has been also found between theoretical and experimental binding energies. A natural bond orbital analysis confirms the role of the π interaction in the metal-carbonyl bond and gives an explanation to the preference for bent structures found in chromium and copper monocarbonyls. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Density functional calculations with large basis sets have been performed for nine conformers of neutral glycine. The results obtained by standard, even gradient corrected functionals are significantly different from the best post-Hartree–Fock computations and the available experimental data. Inclusion of some Hartree–Fock exchange significantly improves matters, thus providing a promising protocol for the study of noncovalent interactions in biomolecules. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations on the geometry and bonding energy of the X - - - I intermolecular interaction of CF3I and (CH3)(sub n)X and (CH3)(sub n)XO are reported. All the adducts with the oxides as donors show a weaker interaction with CF3I than the relative donor without oxygen except the CF3I - - - ON(CH3) adduct, which has a stronger interaction.

The Mn (OESPz) complex reacts with perfluorodecalin or 1,2-difluorobenzene affording the fluromanganese (III) (ethylsulfanyl) porphyrazinato complex and defluorinated organic products. The preliminary results of this investigation concern the use of Mn (OESPz) in the chemical and electrochemical reductive defluorination of perfluorodeclain.

The first expanded campestarenes based on a keto–enamine scaffold have been constructed using uranyl acetate as a template. Macrocycles with six and eight aryl rings in their backbone host dinuclear and tetranuclear uranium(vi) species, respectively. The complexes were characterized by SCXRD, FT-IR, UV-vis, and NMR spectroscopy, and DFT calculations corroborated their structures. [ABSTRACT FROM AUTHOR]

A novel flexible ligand with methyl substituted pyrimidine rings and thioether spacers has been synthesised and the corresponding 1 : 1 silver(i) adducts have been obtained by interaction with different silver(i) salts AgX (where X = NO3−, BF4−, ClO4−, CH3SO3−, CF3CO2−, and CF3CF2CF2CO2−). The X-ray single crystal structure determination of two of the new silver(i) adducts (X = NO3− and CF3CO2−) has proved the formation of coordination polymers with Ag(i) ions almost linearly coordinated to two nitrogen atoms of the pyrimidine rings of the multitopic ligand used. The linear coordination mode shown by the new flexible ligand is induced by the presence of the substituents on the pyrimidine rings, regardless of the type of the AgX salt used in the formation of the respective silver(i) derivatives. This observation represents a neat change in comparison to the already reported series of complexes with unsubstituted (and otherwise identical) ligands, in which dinuclear coordination units have been invariably obtained. Computational investigations have been performed with the aim of explaining such an observed change. A computational comparison of a known dinuclear complex and its related polymeric one has been detailed here and has allowed us to highlight the importance of the introduced substituents in changing the ligand interactions internally to their coordination units and among adjacent units in the solid phases. [ABSTRACT FROM AUTHOR]

The conformational and stereodynamic properties of a pyrene‐substituted ethylthioporphyrazine (PzPy), promising as a dye for organic optoelectronic applications and light‐harvesting systems, have been investigated by DFT computations and variable‐temperature NMR and HPLC. In PzPy, rotation around the pyrene–macrocycle bond is hindered and the molecule displays atropisomerism, existing as a pair of enantiomers, thus representing the first chiral alkyl‐porphyrazine to be reported in the literature. The rotational barrier (ΔG‡ ≈ 22.0 kcal mol–1), measured by variable‐temperature HPLC experiments, allows chromatographic separation of the enantiomers on a chiral stationary phase below 0 °C, whereas racemization spontaneously occurs at room temperature. The absolute configurations of the eluted enantiomers were also determined by computational analysis of their electronic circular dichroism spectra. The influence of alkyl chain length and metal complexation on the molecular stereodynamic properties have also been investigated by studying its novel octylthio derivative (PzPy‐octyl) and PdII complex (PdPzPy), respectively. The latter also is the first example of a PdII–alkylthioporphyrazine complex. Given that PzPy has been used in the preparation of hybrid materials with nanocarbons for optoelectronic applications, the presence of an axial chirality element may play a key role in its interaction with semiconducting chiral nanotubes. [ABSTRACT FROM AUTHOR]

Abstract: A novel pyrene‐substituted thioethyl‐porphyrazine (PzPy) and the formation of supramolecular assembly with nanocarbons demonstrating photoinduced electron transfer ability are designed. As revealed by spectroscopic and electrochemical studies, PzPy displays wide spectral absorption in the visible range, charge separation upon photoexcitation, as well as bandgap and highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) energy values, matching the key requirements of organic optoelectronic. Moreover, the presence of a pyrene moiety promotes attractive interactions with π‐conjugated systems. In particular, theoretical calculations show that in the PzPy the HOMO and LUMO are localized on different positions of the molecule, i.e., the HOMO on the pyrene moiety and the LUMO on the macrocycle. Therefore, HOMO–LUMO excitation gives rise to a charge separation, preventing excitons recombination. Two kinds of noncovalent hybrid composites are prepared by mixing the PzPy with single‐wall carbon nanotubes (SWNTs) and graphene nanoflakes (GNFs), respectively, and used for photocurrent generation through charge transfer processes between PzPy and nanocarbons. Photoconduction experiments show photocurrent generation upon visible light irradiation of both PzPy/SWNT and PzPy/GNF composites (0.78 and 0.71 mA W−1 at 500 nm, respectively), demonstrating their suitability for optoelectronic applications and light harvesting systems. [ABSTRACT FROM AUTHOR]

In their Communication (e202305525), Mark J. MacLachlan use a single Pt-Pt bond to glue two cyclometalated hosts together and generate a flytrap-like molecule. Keywords: Host-Guest Chemistry; Metal-Metal Bonding; Platinum; Redox; Supramolecular Chemistry EN Host-Guest Chemistry Metal-Metal Bonding Platinum Redox Supramolecular Chemistry 1 1 1 07/21/23 20230724 NES 230724 B Supramolecular Chemistry b . This compound traps inorganic ions, assembles and disassembles photochemically, and irreversibly transports guests from solution to the solid state. [Extracted from the article]

Campestarenes are a new family of Schiff-base macrocycles that form selectively in a one-step synthesis. These macrocycles with five-fold symmetry show solvent-dependent tautomerization and dimerization or aggregation. In this paper, we have prepared new soluble campestarenes that do not aggregate. The initial single-crystal X-ray diffraction study of a campestarene reveals that these macrocycles are nearly flat. The tautomeric behavior of the campestarenes has been extensively studied by variable-temperature, multinuclear NMR spectroscopy, UV/Vis spectroscopy, and IR spectroscopy. In polar solvents, such as DMF, the molecules exist predominantly in their keto-enamine form, but the enol-imine tautomer is dominant in non-polar solvents. A detailed computational study of the tautomeric forms of campestarenes provides a theoretical basis for their behavior and corroborates the experimental data. The results of this study give the first comprehensive understanding of the electronic and spectroscopic properties of these pentagonal macrocycles. [ABSTRACT FROM AUTHOR]

The synthesis, structures and photophysical properties of a series of bis-cyclometallated Ir(iii) complexes bearing phenylpyrazole (ppz) cyclometallating ligands and phenanthroline-based ancillary ligands containing thienyl- and bithienylamido groups are reported. All complexes are emissive in solution, while in PMMA films strong emission is observed from the thienylamido substituted complex with no emission from the bithienylamido complex. The bithienylamido substituted complex has an excited state lifetime which is significantly longer than the emission lifetime, attributed to the population of non-equilibrated 3MLCT and 3LC states in this complex. This represents a rare example of this unusual excited state behaviour. DFT calculations show that the emitting 3MLCT state and the dark 3LC state on bithiophene are close in energy and that a large change in the triplet state geometry occurs upon excitation that effectively lowers the energy of the 3MLCT state below that of the dark 3LC state. The low quantum yield of the bithienylamido complex is attributed to a structural rearrangement upon relaxation back to the ground state, opening a non-radiative decay pathway. [ABSTRACT FROM AUTHOR]

A series of novel non-symmetrically substituted mono β-aryl and β-arylethynyl (alkylsulfanyl)porphyrazines and the corresponding Ni(ii) complexes have been prepared by the Suzuki–Miyaura and Sonogashira cross-coupling reactions with the aim to investigate substituent effects on their electronic and aggregation properties. Spectroscopic, electrochemical and computational investigations show that in both aryl and arylethynyl compounds efficient electron transfer between the aryl and macrocycle moieties occurs. The highest perturbation of the porphyrazine π-electron core is provided by strong electron-donating (NMe2) and electron withdrawing (NO2) aryl substituents, which increase and decrease the macrocycle electron density, respectively. Moreover, while in most of the compounds the LUMOs and HOMOs are mainly localized on the porphyrazine ring, in the amino-substituted derivatives the HOMO is localized on the peripheral aryl moieties and the LUMO is localized on the macrocycle. Charge-transfer electronic excitations give rise to absorptions in UV-Vis spectra of both amino- and nitro-substituted compounds. In the former such excitations occur from aryl-localized to macrocycle-localized orbitals, while backward excitations occur in the latter. Therefore, the porphyrazine ring shows an ambivalent behavior, acting as an electron acceptor in the case of the NMe2-substituted compounds and as an electron donor in the NO2-substituted derivative. In these derivatives, even macrocycle mono-substitution provides unconventional “push–pull” systems suitable for NLO. Columnar discotic mesophases are also shown by thio-octyl arylethynyl derivatives, allowing us to envisage the possibility to achieve compounds both suitable for optoelectronic applications and endowed with self-aggregation properties. [ABSTRACT FROM AUTHOR]

A new mechanism for enhanced phosphorescence emission in the solid state (EPESS) in cyclometallated Ir complexes with the general formula [Ir(CN)2(NO)] involving distortion of the six-membered chelate ring of the ancillary ligand is proposed. Photophysical and computational studies show that neither π-stacking nor restricted rotation cause the observed EPESS in these complexes and that ligand distortions in the triplet excited state are responsible for EPESS [ABSTRACT FROM AUTHOR]

Biscyclometallated iridium complexes [Ir(ppz)2(X^Y)][PF6] (X^Y = pyridine imine) have been synthesised. The pyridineimine ligands are prepared in situ during the complexation. The complexes show room temperature emission between 640 and 780 nm in CH2Cl2 solution. The emission is red shifted compared with the analogous bipyridine complex [Ir(ppz)2(bipy)][PF6]. DFT calculations have been used to shed light on the influence of the imine substituent on the electrochemical and photochemical properties. In particular, the calculations suggests that there is a significant change in geometry between the ground state and the first triplet excited state for arylimines but not for alkylimines, leading to much weaker emission for the arylimine complexes. The work demonstrates that pyridineimines can be used as a substitute for bipyridines in luminescent iridium complexes [ABSTRACT FROM AUTHOR]

New (M(R,R'timdt)2) metal-dithiolenes and related compounds, where M = Ni, Pd and Pt and R,R'timdt = monoanion of disubstituted imidazolidine-2,4,5-trithiones, have been synthesized. The characteristics of these compounds are revealed via UV-vis-NIR, FTIR and FT-Raman spectroscopies, CP-MAS 13C NMR and cyclic voltammetry. The physical and chemical properties of the compounds were examined using Hybrid-DFT calculations.

Dinitrodialkoxybenzene derivatives are important precursors for Schiff base macrocycles and a variety of other molecules. During our investigations, we have found that the dinitration reaction of 1,2-dialkoxybenzenes proceeds with unusual regioselectivity, giving exclusively the desired 1,2-dialkoxy-4,5-dinitrobenzene product, but we have been unable to find a good explanation for this result. The dinitration of 1,4-dialkoxybenzene derivatives also exhibits surprising regioselectivity that has hitherto been left unexplained. Herein, we report a detailed DFT analysis of the regioselective dinitration of both 1,2- and 1,4-dimethoxybenzene. These results show that the reaction mechanism likely involves a single electron transfer (SET) process. In the case of the former isomer, the regioselectivity is mainly determined by the symmetry of the HOMO of the aromatic moiety that defines the structure of the SHOMO of the aromatic radical cation formed by the SET process. In the case of the latter isomer, the selectivity is due mainly to solvation effects and may thus be altered depending on the solvent environment. Synthetic studies of the nitration of 1,4-dialkoxybenzene derivatives using different solvent conditions support this conclusion and provide practical information for tuning the regioselectivity of the reaction. [ABSTRACT FROM AUTHOR]

A computational investigation about the Lewis acid–base adducts between bases Cp2MH2 (M = Mo, W) and acids BX3 (X = F, Cl) and Al(CH3)3 is presented. Density functional methods based on pure and hybrid correlation-exchange functionals and relativistic corrections based on the zero order relativistic approximation (ZORA) have been applied. A comparison with experimental data has been addressed to give insights about the nature of the acid–base interaction with the aim to evaluate the role of the transition metal in charge donation toward the acid centre. In this respect, the likelihood of proposed criteria for recognizing the presence of transition-metal direct charge donation has been discussed. [ABSTRACT FROM AUTHOR]

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The properties of mixtures of two polysaccharides, arabinogalactan (AG) and hyaluronic acid (HA), were investigated in solution by the measurement of diffusion coefficients D of water protons by DOSY (Diffusion Ordered SpectroscopY), by the determination of viscosity and by the investigation of the affinity of a small molecule molecular probe versus AG/HA mixtures in the presence of bovine submaxillary mucin (BSM) by 1HNMR spectroscopy. Enhanced mucoadhesive properties, decreased mobility of water and decreased viscosity were observed at the increase of AG/HA ratio and of total concentration of AG. This unusual combination of properties can lead to more effective and long-lasting hydration of certain tissues (inflamed skin, dry eye corneal surface, etc.) and can be useful in the preparation of new formulations of cosmetics and of drug release systems, with the advantage of reducing the viscosity of the solutions. [ABSTRACT FROM AUTHOR]